An ink-jet printer has an ink-jet head for discharging ink and an ink cartridge for supplying ink to the head. For smooth ink supply to the ink-jet head, the ink cartridge has an atmosphere-communicating passage through which atmospheric air flows into the ink cartridge. The amount of atmospheric air flowing into the ink cartridge is equivalent to the amount of ink flowing out through the supply port of the ink cartridge. However, the communication between the inside of the ink cartridge and the atmosphere by the atmosphere-communicating passage causes the ink in the cartridge to evaporate gradually and becomes viscous. This changes the volume of the ink droplets discharged through the nozzles of the ink-jet head and the speed at which the droplets are discharged, thereby lowering the printing quality. Therefore, for example, an ink cartridge (an ink tank) which has a narrow and labyrinthine atmosphere-communicating passage, which is capable of decelerating ink evaporation has been proposed (for example, see Patent Document 1).    Patent Document 1: Japanese Patent Application Laid-open No. 11-105305 (FIG. 1)